1. Field of the Invention
The invention relates to a sealing means for closures, especially sealing means for closures for packages for liquids such as beverages. In particular the invention relates to a sealing means for containers for carbonated liquids such as soft drinks but is well adapted to seal other containers such as glass or PET containers with contents at above or below atmospheric pressure or having gaseous components or requiring a hermetic seal. The invention further relates to a closure and a process for making and applying of a sealing means, respectively a closure.
2. Description of the Art
Seals of closures are generally manufactured from several types of plastic, such as Polyethylene (from now on PE) or Polypropylene (from now on PP) or EVA-based materials such as Darex™ liner material. The latter is mainly used for the manufacture of liner closures; the material is less hard and less durable than PE. Softer material such as Low density PE (LDPE), ethylene vinyl acetate (EVA) or compounds based on polyolefine raw materials are often used as sealing material. More rigid materials such as Polypropylene are often used as a shell material of closures.
From prior art a vast amount of documents is available which are directed to closures and caps for sealing of containers. A selected range is explained subsequent.
EP0076778 of Albert Obrist AG was filed in 1982 and is directed to a closure cap made of plastics material which has a circular outer sealing lip having a thickness which continuously decreases versus its free end. The outer sealing lip is arranged in the region of the joint between an outer vertical skirt and a disc like top portion and points obliquely inwards. At its smallest diameter, the sealing lip has a rounded sealing portion. Below the sealing portion the sealing lip is widened outwards in the manner of a funnel to receive a container opening. However, due to the obliged arrangement of the sealing lip the sealing lip often tends to be distorted during application, especially crooked application onto a neck of a container. A further disadvantage consists in that due to the inclined arrangement this seal is relatively rigid and therefore not very good in adjusting in lateral direction.
U.S. Pat. No. 4,489,845 was filed in 1984 and assigned to Albert Obrist AG. U.S. Pat. No. 4,489,845 is directed to a screw-cap for closing a container opening. The cap has a sealing lip which is affixed to the cap top. The inner side-wall of the outer sealing lip has a diameter which is greater than the outer diameter of the container outer wall. A clamping device, which can be designed as an inner seal, creates a contraction of the cap top when the screw-cap is screwed onto the container due to deformation of the outer shell of the closure, by which means the sealing lip shall be pressed against the container mouth. In this manner the sealing lip is only pressed radially against the container mouth during the course of the screwing-on process. Thereby over-stretching and damage to the material of the sealing lip shall be prevented. In an engaged position the sealing lip engages around the upper outer rim of the neck of a container opening. One disadvantage is that the described deformation of the closure is related to extensive operating forces. A further disadvantage consists in that the outer shell tends to break due to extensive stress and deformation (stress cracking) which results in complete failure of the closure and loss of the product.
EP0114127, filed in 1984, of Continental Whitecap and EP0176205, filed in 1985, of Sun Cost Plastic both disclose a seal having two sealing flaps arranged in general V-shape. When the closure is drawn down onto a container, the flaps will deform in accordance with the cross section of the sealing surface area of the container including down inside of the mouth of the container and down along-side the exterior surface of the neck finish to provide effective sealing contact with the container sealing area. The sealing flaps are in engaged position laterally supported and pressed against the neck of the closure.
EP0529383, filed in 1992 by Jacob Berg GmbH, is directed to a plastic screw cap for containers, in particular pressurised beverage containers. The closure comprises an annular sealing strip which is integrally moulded with the shell of the closure. Adjacent to the sealing strip a bead is arranged pressing the sealing strip against an upper outer edge of the neck of a container. One disadvantage consists in the reduced lateral adjustability.
EP0770559, filed in 1996 by Sacmi Cooperativa Meccanici, is directed to a plastic screw cap with a liner made by compression moulding. The closure comprises an annular lip that is designed to support a liner and protrudes from the disk-like portion concentrically with respect to the cylindrical outer wall. The annular lip is acting as a shoulder for a sealing liner, so that the liner, when the cap has been applied to the container, engages to the rim of the mouth of the container.
U.S. Pat. No. 4,489,844 was filed in 1982 and assigned to Charles A. Breskin Assoc. Inc. is directed to a reusable cap for closing carbonated beverage containers or the like. The closure consists of an internally threaded shell having a fitment therein which sealingly engages the neck of the beverage container at the free edge thereof. The shell and the fitment are constructed of different plastic materials and are injection moulded in different portions of the same moulding cavity. First, the fitment is formed and then, without moving the fitment from the position in which it was formed, the shell is formed, to produce a unitary structure in which substantial portions of the fitment are imbedded in the shell.
U.S. Pat. No. 5,447,674 filed in 1993 by Frank Schellenbach is directed to a method and a mould core for the production of two-component injection moulded plastic closure. A mould core for use in a two-component injection moulding method is presented for two-component injection moulding of plastic closures for containers. The mould core consists of first and second sub-core. After injecting the first substance, one sub-core or tool element is displaced by a predetermined amount relative to the first moulding. One disadvantage of the described procedure is that displacement of the core can only take place when the material of the first stage has sufficiently congealed which results in a significant delay. A further disadvantage consists in that the geometry of the closure and the seal is significantly restricted due to the mould function. A still further disadvantage is that the seal may not comprise a radial protrusion which would result in an undercut the mould because displacement of the mould core would not be possible anymore.
WO03011699 filed in 2002 by Bericap is directed to a closure cap comprising an internal sealing skirt which is substantially truncated and converges from the sealing skirt base towards the free end of the sealing skirt. The inside of the sealing skirt is designed to cooperate with the outside of the neck. The internal diameter of the sealing skirt towards its free end portion is designed smaller than the external diameter of the neck. As described the closure can comprise an annular v-notch designed to improve attachment of a liner to the rim of the neck or contact between the liner and the rim.
From the inventor of the herein disclosed invention a series of closures for carbonated beverage containers is known and described among others in WO99/03746 (1998), WO99/03747 (1999), WO89/12584 (1989), WO03/022701, WO00/56616, WO/56615. The seals of these closures are all having in common that an annular sealing rib, which initially is projecting downwardly and inwardly with respect to the top portion of the closure, is turned inside-out during application onto a neck of a container.
A problem of closures known from prior art is that the seal of these closures often fails at high internal pressure and content leaks due to doming or lift-off of the top portion of the cap. Especially with caps which seal primarily on the inner peripheral surface or on the annular top surface of the neck of the container this problem may occur. A further problem often occurring with closures known from prior art is leakage of the seal due to high internal pressure in the container and additional top load applied to the top of the closure, e.g. due to stacking of several containers. The reason for this can be found in deformation of the closure and therewith related displacement of the seal. A further problem of the closures known from prior art is that the seal fails due to crooked application of the closure onto a neck of a container.
It is an object of the present invention to provide a sealing means for closures, especially closures for containers for carbonated beverages and other hot or cold liquids, which has an improved capability to adapt to necks of containers, especially necks of containers having a certain imperfection or damage.
It is a further object of the present invention to provide a sealing device and closure suitable for carbonated beverages and other hot or cold liquids, to offer advantages in production such as low cycle time and less material consumption and to be still pressure tight at high internal pressures and top load.